All such meetings are surrounded by hyperbole, for which my own trade shares its responsibility, disingenuousness and even dishonesty. But last week's was an object lesson in how in subsequent discussions of things that aren't true, or are half true, are accepted as facts. Here are a few.

Prime Minister David Cameron's "veto" prevented powers from being relinquished from London to Brussels.

No. The proposal was to allow treaty changes so that euro-zone member countries, and any other government that chose to follow the same rules, would more tightly coordinate their budgets and government debts and be subject to near-automatic discipline if they didn't comply. There was never any question of the U.K. being subject to these rules.

Britain was seeking an opt-out for EU regulation on financial services.

No. It was suggesting a unanimous vote on certain financial-services issues, rather than the qualified majority vote. According to the paper, which was first obtained by the Daily Telegraph, these issues included transferring further supervisory powers from national to EU agencies, any actions that affect tax revenues or substantial levies on the financial sector.

It also sought other guarantees, including "no discrimination within the single market for financial services on the grounds of the member states in which an institution is established." (This is an effort to challenge the European Central Bank policy insisting on clearing houses being in the euro zone and thereby having access to ECB credit.)

The nearest thing to a proposed opt-out, says Mats Persson of the euro-skeptic think tank Open Europe, was an effort to secure exemption from some EU regulations for businesses (say, hedge fund managers) from outside the EU that only operate in one country.

Britain was seeking to block a financial-transactions tax.

No. It already has a veto on that.

Britain was seeking weaker regulation for its banks.

No. One thing it wanted the freedom to do was impose tougher capital requirements on U.K. banks—an area where the European Union is looking to introduce maximum requirements. Britain wanted the right "to impose higher capital requirements on certain institutions to reflect the potential call on U.K. taxpayers of the U.K.'s large and international financial sector," the paper said.

French President Nicolas Sarkozy was indignant at British behavior.

He may have pretended to be, argues David Marsh, an author and expert on the euro, but Mr. Cameron helped him out of a tight spot. France never wanted a treaty enforced by the European Commission and the European Court of Justice that was backed by Germany, preferring governments to police their own affairs.

Beyond that, France has made no secret of its desire for decision-making among the 17 euro-zone members and sidelining the British.

"Sarkozy can now cast Britain as the scapegoat for blocking a treaty he never wanted. Vive David Cameron! Give that man the Legion d'Honneur!" Mr. Marsh wrote in a commentary for the Official Monetary and Financial Institutions Forum, a private organization that brings together sovereign-wealth funds and central bankers.

Britain is now adrift from the rest of the EU.

Mr. Cameron's tactics don't appear to have been very effective: He burned political capital in return for nothing. But, Britain's longer-term relations with the EU hang to some extent on what happens now, says Mr. Persson of Open Europe.

The U.K still will have to be involved in discussions, for example, about how the European institutions are used to police this proposed accord, which will give him leverage. As my colleague, Laurence Norman reported Thursday, the British will get a seat at the top table on the summit due in late-January or early-February to discuss these matters.

Mr. Cameron hasn't recanted of his decision, but he has spent some of the past week talking to other European leaders, and his officials say he plans to do more.

It is not after all in British interests to undermine the euro zone, whose troubles remain a paramount concern for the British economy. Seven of the top 10 British export markets are in the euro zone.

Euro-zone borrowers owed British banks more than $1 trillion at the end of June, according to Bank of England data, with borrowers in France leading the pack at $292 billion. Of the currency area's more troubled economies, Irish borrowers owed $157 billion while debts owed by borrowers in Italy, Spain, Greece and Portugal together exceeded $215 billion.

In the end, though, there are more important questions than whether Britain will help or hinder this agreement in coming months. It's really whether the agreement will help resolve the euro's debt crisis.

Like many others, Mr. Marsh doesn't accept the German argument that the issue the accord addresses—budget indiscipline—is the main cause of the crisis. If it is, he asks, why are Spain and Ireland, which ran budget surpluses in 2007, in trouble?

"At the root of the euro upheaval is a balance of payment crisis caused by the cumulative effects of a 13-year-old one-size-fits-all monetary policy and a fixed exchange rate for a collection of disparate countries in very different stages of economic and structural development," he argues.

That means the agreement may be a step in the right direction, he says, "but is neither necessary nor sufficient to bring calm" to the euro area.

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